pantie, panty, scanty, step-in -- (short underpants for women or children (usually used in the plural))
Overview of verb step-in
The verb step in has 2 senses
intervene, step in, interfere, interpose -- (get involved, so as to alter or hinder an action, or through force or threat of force; "Why did the U.S. not intervene earlier in WW II?")